The purpose of the proposed research is to identify the endocrine and neuroendocrine responses to priming pheromones that modify the onset of puberty. In the housemouse and several other species a urinary pheromone from adult males accelerates the onset of puberty in juvenile females and a urinary pheromone from females in a group inhibits the onset of puberty. We know a good deal about the endocrine response to the male stimulus but little about the female inhibitory stimulus. Under natural conditions, puberty inhibition is an important factor regulating reproduction and population dynamics. Thus, it is essential that the basic response mechanism to puberty inhibiting pheromone in the recipient female is understood. The specific experiments proposed will test: (1) whether urine from grouped females causes the same endocrine changes as the presence of a group of females, (2) whether the inhibitory effect is the result of pituitary unresponsiveness to LHRH, (3) whether the steroid hormone positive feedback mechanism is involved, (4) whether male and female pheromonal cues alter neurotransmitter levels in specific brain areas, and (5) whether induction of early or late puberty by pheromones can have lasting influences on endocrine responsiveness during adult cycling.